That assessment, it says, is based on what has happened at similar high-profile events.

The analysis, sent this week to local police organizations nationwide by the FBI and Department of Homeland Security, says these groups "probably lack the capability to overcome the heightened security measures" around actual convention facilities but could target businesses or means of transportation nearby. Most of what these groups do, the bulletin says, involves vandalism, trespassing and attempts to block roads. But it says they're becoming more interested in trying to use explosives.

The Republican national convention is scheduled to run Monday through next Thursday in Tampa, Fla. The assessment says the FBI picked up information in mid-March indicating that some anarchists from New York were planning to go to Tampa in hopes of closing "all the Tampa Bay-area bridges" during the convention, although it doesn't say how they planned to do it.